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Specifications for the World's 2nd Smallest Midi Synth
E3V3A Posted: 10 Jan 2019, 03:01 PM
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I've been looking the ATtiny85 and ATtiny2313 projects with great interest, and it seem that it should require very little improvement to the chips used, in order to get quite useful polyphonic + full pitch-bend and possibly with a few different wave-forms.

What kind of similar chips would we need to accomplish this?
Perhaps there are already other project doing this that we can use, simplify and improve upon?

I suggest we use USB as midi input and the regular (stereo?) phone jack (from before) as output. Also USB provides 5V so batteries are not needed.

* What is an acceptable list of synth related criteria for such a project?
* What would be an acceptable list of hardware criteria?

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mit Posted: 10 Jan 2019, 04:01 PM
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yeah whatever

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Hello.

QUOTE (E3V3A)
polyphonic + full pitch-bend and possibly with a few different wave-forms

Different waveforms is going to be a challenge in the current method (pin toggling). You need analog output for anything other than square and pulse waves.

If you are planning to run it from USB though, there are none of the limitations that powering it from MIDI-DIN imposes, you could throw a much more powerful chip on board (such as an STM32) and make your life much easier.

QUOTE (E3V3A)
list of hardware criteria

Hardware USB support, DAC output if possible. To fit it inside a USB plug you want a part with a very low pin count in a surface mount package.


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DAVID Posted: 10 Jan 2019, 10:01 PM
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avrs + midi = best diy synths

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QUOTE (E3V3A)

I suggest we use USB as midi input and the regular (stereo?) phone jack (from before) as output. Also USB provides 5V so batteries are not needed.
or instead of using the smt32 you can use an arduino micro/leonardo for usb (i don´t recommend using V-USB because it is pretty likely to crash) and just modifying my code from tha 4 voice polyphonic arduino midi synth https://mitxela.com/forum/topic/arduino-midi-synth-now-with-5-different-wave-forms


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E3V3A Posted: 11 Jan 2019, 07:01 AM
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The Arduino Micro look very nice, but then we are leaving the realm of worlds smallest, since we'd need external power and using a full blown microcomputer.

Instead I was thinking along the lines of ATtiny1614 or similar to be able to maintain the super compact form-factor of the 2313 project.

The 1614 has:
20 MHz
16 KB
2048 SRAM
1 UART
6 PWM
1 x 8-bit, 3 x 16-bit Timers


However, I don't understand the device operation enough to properly evaluate. So perhaps it's not enough? From the video & description of the 2313 project, it seem to be the clock and number of timers that was the limiting factors?

Hardware:
https://en.wikipedia.org/wiki/ATtiny_microcontroller_comparison_chart
https://www.microchip.com/wwwproducts/en/ATtiny1614 ?


Last edit by E3V3A at 11 Jan 2019, 07:01 AM

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DAVID Posted: 12 Jan 2019, 04:01 PM
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avrs + midi = best diy synths

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The ATtiny1614 seems like a very nice mcu in contrast to the attiny2313 but for being a usb synth that you want to create you must port the V-USB library to that device that i think it would not be that fun.
Also if you use V-USB as i said to play midi files (note: if you use some program like Virtual Midi Piano Keyboard/VMPK you can send midi notes since that is a light task) will be to slow to handle the instruments commands that are sent at the beginning and just crash.

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